Log propagated request ID and allow interoperability with legacy tracing

[hslatman]

This adds a new requestid package, which can be used to propagate the request ID (using the new logic) to the legacy logging functionality. The old request ID will now be logged only if the new request ID could not be retrieved from the context.

It's likely this will only have to be used (by dependent systems) for a short while, since panoramix implements our new logging and tracing functionality.

[maraino]

I would say to use one or the other, adding preference to the new one. The client side of grpclog should also support sending the request id to the server.

[hslatman]

I would say to use one or the other, adding preference to the new one. The client side of grpclog should also support sending the request id to the server.

I view this as a temporary solution. When our observability stack is implemented more broadly, we can drop logging. Currently we still kind of need both, so that's why I think it makes sense to have them both for now.